JP2023504824A - Plant for melting and/or heating metallic materials and method for supplying power to said plant - Google Patents

Abstract

The embodiments described herein melt and/or heat a metallic material (M) comprising a furnace (11), an electrical energy supply means (13) and a power device (12) connected therebetween. about the plant for The invention also relates to a related method of feeding a plant (10) for melting and/or heating. [Selection drawing] Fig. 1

Description

The present invention relates to a plant for melting and/or heating of metallic materials comprising an electric furnace and a power unit suitable for supplying high ohmic inductive loads of 100 MW or more.

Embodiments described herein also refer to power supply methods for melting and/or heating plants.

In particular, the invention relates to the steel industry and the field of steel production in which electric furnaces, such as electric arc furnaces, ladle furnaces, submerged arc furnaces, melting or refining furnaces, induction melting or induction heating furnaces, are used for melting metallic materials. , or other metal or vitreous material processing areas.

There are known plants for heating and/or melting metallic materials, which include an electric furnace into which the material to be melted is introduced and one or more electric furnaces which obtain energy from the electrical grid and supply it. A power unit is included.

The types of electric furnaces of the present invention can be selected from the group consisting of electric arc furnaces, submerged arc furnaces, ladle furnaces, and generally melting furnaces, smelting furnaces, heating furnaces, induction furnaces.

These electric furnaces typically operate as non-uniform ohmic inductive loads. This is because the power required and absorbed varies depending on the processing stage or the type of metal material used.

From patent EP-B-3124903 in the name of the applicant a power supply for an arc furnace is known which includes a device for positioning the electrodes and a regulating group including a plurality of converters. Selectively controllable to adjust electrode voltage and supply current.

The power device described in EP-B-3124903 therefore acts like an adjustable current generator, supplying the power required to power the electric arc furnace and the process in which it is being performed. (insertion, casting, purification). Thus, the solution of EP-B-3124903 is limited only by the parameters of the equivalent circuit, which vary with process steps, unlike conventional solutions in which the transformer acts as a voltage generator and cannot control the current. be.

In the power device described in EP-B-3124903 the current and voltage of the arc are individually regulated to significantly limit current fluctuations during the first phase of the process, the insertion phase, and subsequent fusion and It can actually be stabilized during the purification stage.

Both the power device described in EP-B-3124903 and the conventional power device are normally powered by three-phase mains current supplied by the public electricity network.

WO2019/207609 describes a melting apparatus and method in an electric arc furnace using a three-phase feed current supplied by a traditional electrical grid.
The apparatus comprises a transformer, a plurality of rectifiers connected to the transformer, and a plurality of converters connected on one side to the rectifiers and on the other side to the electrodes of the electric arc furnace.

Italian Patent Application No. 102009901751919 describes an apparatus for powering home user equipment by coupling a primary power supply to one or more auxiliary power supplies.

US Patent Application Publication No. 20190018437 discloses an electrical energy delivery system comprising a primary transformer, a secondary transformer, and a controller that controls a regulated signal generator to apply a regulated power signal to the transformer secondary. The supply system is described and includes an auxiliary power supply connected to the primary of the transformer.

For example, melting and/or heating plants used in the production of steel in the steel sector require a high power supply of tens of megawatts (MW), especially 30 MW to 200 MW, to the furnace, depending on the size of the plant and/or furnace. requires.

Therefore, in order to obtain sufficient energy supply, the melting and/or heating plant must be continuously connected to the grid.

Furthermore, since the absorption of three-phase alternating current depends on the output, the more melt produced in the furnace, the greater the amount of electrical energy that must be purchased.

A drawback of conventional solutions is the need for a permanent connection to the public power grid.

Another drawback is that, especially in some regions, the consumption of electrical energy can be expensive, or after a significant socio-economic event, the estimated cost of power supply is likely to rise significantly.

Various steel mills are therefore forced to limit production, for example, at night when the cost of electricity supplied by the grid is low.

Furthermore, if a power grid outage can occur, it is necessary to shut down the plant and production with the problem of lost productivity and thus delayed delivery of production batches.

Accordingly, there is a need for improved apparatus for heating and/or melting metallic materials that can overcome at least one of the shortcomings of the prior art.

In particular, it is an object of the present invention to provide a melting and/or heating plant for metallic materials that can operate at least partially independent of the electrical grid in order to reduce energy supply costs and thus production costs. .

One purpose is also to reduce the risk of shutdown of the treatment plant due to power grid outage events, which in severe cases can take days.

Another objective is to reduce energy consumption from and on the public grid.

A further object is to provide a method of supplying a plant for heating and/or melting of metallic materials, which makes it possible to limit the supply of electricity by the grid.

It is also an object to allow operation of the heating and/or melting plant for metallic materials during the day and/or at night.

A further advantage and benefit provided by the present invention is also that it allows for the reduction of _CO2 emissions or other related emissions when the production of energy by the public grid is not entirely generated by renewable energy sources.

To overcome the shortcomings of the prior art and to obtain these and further objects and advantages, Applicants have studied, experimented and practiced the present invention.

The invention is expressed and characterized in the independent claims. The dependent claims present other features of the invention or variants of the main solution.

In view of the aforementioned objects, embodiments described herein relate to a plant for melting and/or heating metallic materials comprising a furnace into which metallic materials can be introduced, electrical energy supply means, and at least one power unit. A power unit is connected between the electrical supply means and the furnace and is suitable for powering the furnace with the desired voltage and current.

According to embodiments, the power device includes:
- a transformer connected to a distribution network and configured to receive an alternating primary voltage and primary current and convert them into an alternating secondary voltage and an alternating secondary current;
- a plurality of rectifiers connected to a transformer and configured to convert the alternating secondary voltage and secondary current into a direct current and a direct intermediate current;
- a plurality of converters connected on the one hand to the rectifier and on the other hand to the load, ie the electric furnace, and arranged to convert the DC intermediate voltage and the intermediate DC current into an AC supply voltage and an AC supply current.

According to embodiments, the power device also includes a control and command unit configured to control and command the operation of the converter and to adjust the supply voltage and supply current to the load over time.

According to an embodiment, the melting and/or heating plant is connected to a power unit to supply electrical energy for powering loads additionally or alternatively to the electrical energy supplied by the electrical grid. at least one alternative energy source separate from the electrical grid, configured in a power grid.

Thanks to the alternative energy source, the melting and/or heating plant can be powered at least partially independent of the grid and, in some cases, the melting and/or heating plant can be disconnected from the grid at least temporarily. In any case, the supply of energy from the grid can be scaled back according to the daily timeframe, possibly restricted to times when it is less expensive.

Furthermore, the existence of alternative energy sources allows the melting and/or heating plant to be used even in the event of grid malfunctions or blackouts.

According to embodiments, alternative energy sources may include renewable energy sources suitable for providing energy selected from, for example, solar energy, wind energy, or hydroelectric energy.

According to a possible variant, the alternative energy source may be a non-renewable energy source derived from burning fossil fuels, such as oil, coal, gas.

According to embodiments, the alternative energy source may comprise an alternating energy source configured to provide alternating voltage and current.

According to a possible embodiment, the alternating energy source comprises a hydroelectric power plant or a dam suitable for producing hydroelectric power or a wind farm containing at least one turbine suitable for supplying wind energy. can be done. Dams, hydroelectric power plants and wind power plants can be equipped with alternator devices suitable for converting the respective renewable energy produced into alternating voltage and current for supply to power installations.

According to embodiments, the alternative energy source may include a DC energy source configured to supply DC voltage and DC current.

According to embodiments, the DC energy source may include, for example, a photovoltaic plant including a plurality of photovoltaic panels.

By virtue of the structure of the power device, both AC and DC energy sources are connected to the power device by changing the alternative energy input point to the power device each time, without the need for additional dedicated components or systems. Is possible.

According to embodiments, the AC energy source may be directly connected to the transformer of the power device. In this way, the downstream rectifier rectifies the AC voltage and current, supplies DC current and DC voltage, which feeds the converter to obtain the supply voltage and supply current.

According to embodiments, the DC energy source can be connected to a DC intermediate circuit located downstream of the rectifier. This is because there is no need to provide any step of rectifying the DC energy, it can be fed directly to the converter for conversion into supply voltage and supply current.

According to embodiments, electrical components configured to ensure unidirectionality of the generated current may be provided between the DC energy source and the DC intermediate circuit. This prevents incorrect polarity of the input current from damaging the power device components.

According to embodiments, two or more alternative energy sources of the same or possibly different forms may be provided.

For example, a first alternative energy source comprising an alternating current energy source connected to a transformer of the power unit and a second alternative energy source comprising a direct current energy source connected to an intermediate circuit may be provided.

According to a further embodiment, the power device has at least one connection interface for connecting with the electrical grid and at least one connection interface for connecting with one or more alternating and/or direct energy sources. , can be provided.

According to embodiments, the melting and/or heating plant detects and monitors the conditions of the electrical grid and the at least one alternative energy source and, depending on the detected conditions and/or the amount of energy required at each time by the load, There may also be a management unit configured to determine whether to use one, the other, or both to power the power device and the load.

Therefore, it is an advantage to be able to maintain operation of high power loads when the energy available from at least one alternative energy source is low, or when the utility grid fails.

Advantageously, the management unit selects one of: the availability of energy supplied by the grid, the energy costs and the degree of integration of the available energy by at least one alternative energy source to cover the energy demand of the load. The above parameters can be detected.

In this way, based on energy costs, the optimal energy source can be selected at any time, ie energy supplied from the grid or energy supplied from at least one alternative energy source. Therefore, there is no need to cut production or shut down processing plants in the event of energy shortages or excessive costs.

According to a further embodiment, at least for the use of renewable energy sources, it is connected between at least one alternative energy source and the power equipment, allowing storage of self-generated energy in the absence of demand from the furnace or load. An electrical energy storage device can be provided that is configured to:

The stored energy can be used later, for example when alternative energy sources are not available or cannot provide enough energy.

The invention also relates to a method of supplying a heating and/or melting plant of metallic material supplying the furnace by at least one independent alternative energy source different from the electrical grid.

These and other aspects, features and advantages of the present invention will become apparent from the following description of embodiments given as non-limiting examples, with reference to the accompanying drawings.

1 is a schematic diagram of a metallic material heating and/or melting plant according to embodiments described herein; FIG. 1 is a schematic diagram of a heating and/or melting plant with an alternative AC energy source according to embodiments described herein; FIG. FIG. 4 is a schematic diagram of a heating and/or melting plant with an alternative AC energy source according to a variant embodiment; 1 is a schematic diagram of a heating and/or melting plant with an alternative AC energy source according to embodiments described herein; FIG. FIG. 4 is a schematic diagram of a heating and/or melting plant with an alternative direct current energy source according to a variant embodiment; FIG. 4 is a schematic illustration of a heating and/or melting plant according to a variant embodiment; Figure 5 is a schematic view of a variant of the plant of Figure 4;

For ease of understanding, the same reference numbers have been used, where possible, to identify the same common elements in the figures. Elements and features of embodiments may be conveniently incorporated into other embodiments without further recitation.

DESCRIPTION OF EMBODIMENTS Reference will now be made in detail to possible embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of illustration of the invention, and is not intended as a limitation of the invention. For example, one or more of the illustrated or described features, because they are part of an embodiment, can be changed or adopted in or in connection with other embodiments to produce further embodiments. be able to. It is understood that the invention includes such possible modifications and variations.

Embodiments of the present invention relate to a metal material melting and/or heating plant 10 comprising an electric furnace 11 and a power unit 12 suitable for powering the electric furnace 11 .

According to embodiments, power unit 12 may be configured to supply a three-phase load.

According to an embodiment, the melting and/or heating plant 10 comprises electrical energy supply means 13 arranged to supply electrical power to the power unit 12 .

The electrical energy supply means 13 comprise at least one connection 14 to the grid 15 for supplying grid alternating voltage Ur and alternating current Ir.

According to embodiments, the electrical grid 15 may be three-phase.

According to embodiments, grid voltage Ur and grid current Ir may have a predetermined grid frequency fr.

According to a possible solution, the grid frequency fr is a value chosen between 50 Hz and 60 Hz. That is, it is based on the frequency of the grid of the country in which the furnace 11 is installed.

According to an embodiment, the electrical energy supply means 13 comprise at least one independent alternative energy source 16 different from the grid 15 .

According to embodiments, the alternative energy source 16 is separate from the electrical grid 15 and directly connected to the power unit 12 . A “direct” connection means that the alternative energy source 16 supplies energy to the power device 12 without interacting with the electrical grid 15 and thus without going through the connection 14 with the electrical grid 15 .

According to embodiments, the furnace 11 of the form in question is suitable for use in electric arc furnaces, electric submerged arc furnaces, induction furnaces, ladle furnaces or in general in steel plants for steel production or in plants for glass production. It can be a melting furnace or a refining furnace or an induction heating furnace.

In the following description reference is made by way of example to an electric arc furnace 11 comprising a vessel 17 or bath into which the metallic material M to be melted is introduced.

Furnace 11 is also provided with a plurality of electrodes 18, in the illustrated example three electrodes 18 arranged to induce an electric arc through the metal material M to melt it. .

According to an embodiment of the present invention, the electrodes 18 are mounted on a moving device 19 configured to selectively move the electrodes 18 towards/away from the metallic material M.

Movement device 19 may include mechanical actuators, electrical actuators, pneumatic actuators, hydraulic actuators, articulated mechanisms, mechanical kinematic mechanisms, similar and equivalent elements, or any possible combination of the foregoing. A group containing at least one can be selected.

According to a possible embodiment of the invention, if the number of electrodes 18 is three, each of the electrodes 18 is connected to a respective power supply phase of the power device 12 .

According to an embodiment, the power unit 12 receives energy supplied by the power supply means 13 , i.e. the electricity grid 15 and/or the alternative energy source 16 , and converts it to certain electrical parameters suitable for powering the furnace 11 . It can be converted into a supply voltage and a supply current with "Ua", "Ia", "fa".

According to an embodiment, the power device 12 comprises at least one transformer 20 connected to the electrical grid 15 and configured to transform primary alternating voltage and current into secondary alternating voltage and current.

According to possible embodiments, transformer 20 may include a transformer primary 21 magnetically coupled to at least one transformer secondary 22 .

According to possible embodiments of the present invention, transformer 20 may include a plurality of transformer secondary sides 22 magnetically coupled to transformer primaries 21 . This makes it possible to reduce the influence of disturbances exerted on the distribution network side, that is, reduce the harmonic components and reactive power exchanged with the distribution network 15 .

The secondary electricity supplied by the transformer 20 has a secondary voltage Us, a secondary current Is and a secondary frequency fs that are predefined and set by the design characteristics of the transformer 20 itself.

In particular, the secondary frequency fs may be substantially equal to the aforementioned electrical grid frequency fr identified above, and may generally be equal to the primary frequency fp of the current circulating in the transformer primary 21 .

The secondary voltage Us, the secondary current Is are, instead, respectively the voltage of the grid Ur, the current of the grid Ir, or generally the primary voltage Up and from the transformation ratio of the transformer 20 itself to the primary current Ip of the transformer primary 21 can relate.

For example, a multi-tap transformer 20 may be provided with an adjuster (not shown) provided to selectively adjust the electrical conversion ratio of the transformer 20 in relation to particular needs.

The power device 12 according to the invention also includes a plurality of rectifiers 23 connected to the transformer 20 and configured to convert the alternating secondary voltage and current into continuous intermediate voltage and current.

Specifically, the rectifier 23 makes it possible to rectify the AC secondary voltage Us and the AC secondary current Is into the respective DC intermediate voltage Ui and DC intermediate current Ii.

The rectifiers 23 can be selected in groups including diode bridges and thyristor bridges.

According to a possible embodiment, the rectifier 23 is e.g. (Bipolar Junction Transistor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), IGBT (Insulated Gate Bipolar Transistor).

According to an embodiment, power device 12 comprises a plurality of converters 24 connected to rectifiers 23 and configured to convert DC voltages and currents to AC voltages and currents that feed electrodes 18 .

According to possible embodiments, the converter 24 may include, for example, SCR (silicon controlled rectifier), GTO (gate turn-off thyristor), IGCT (integrated gate commutation thyristor), MCT (metal-oxide semiconductor controlled thyristor), BJT ( Bipolar Junction Transistor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), IGBT (Insulated Gate Bipolar Transistor).

According to a possible embodiment of the invention, the adjustment device 26 can, by way of example, only include a hysteresis modulator, or a PWM (Pulse Width Modulation) modulator.

These forms of modulators can be used to control the rectifier 23 and converter 24 semiconductor devices. These appropriately controlled modulators generate voltage or current values that are supplied to the furnace 11 , in this case the electrodes 18 .

According to a possible embodiment, the rectifier 23 can be connected to the converter 24 by at least one intermediate circuit 27 operating at least on direct current.

The intermediate circuit 27 stores DC electrical energy and creates a separation between the rectifier 23 and the converter 24 and thus at least from the grid 15 or is connected upstream of the intermediate circuit 26 with respect to the furnace 11 . It can be configured to be separate from any possible alternative energy source 16 .

In particular, process-induced rapid power fluctuations are partially filtered through the intermediate circuit 27 to reduce their impact on the grid side 15 .

Rectifier 23 , converter 24 and intermediate circuit 27 may form a DC unit 28 . In particular, DC unit 28 may comprise the DC components of rectifier 23 and converter 24 .

For example, according to embodiments described with reference to FIGS. 2 and 3, the at least one alternative energy source 16 is an alternating electrical energy source 31 configured to provide an alternating voltage U _AC and an alternating current I _AC . Prepare.

According to embodiments, an alternating energy source 31 is connected to the transformer 20 .

According to a preferred embodiment, a source of alternating electrical energy 31 is connected to the transformer primary 21 . In this case, the alternating voltage U _AC alternating current I _AC is transformed by transformer 20 , rectified by rectifier 23 and converted by converter 24 .

According to a further embodiment, it is also possible to connect a source of alternating electrical energy 31 to each transformer secondary 22 or to each transformer secondary 22, in which case the secondary voltage Us and the secondary current Is are , which has desirable properties.

According to embodiments, AC power source 31 may include a renewable energy source.

According to a possible solution, the renewable energy source may comprise a hydroelectric power plant or a dam 32 suitable for converting hydroelectric energy into electrical energy.

According to another embodiment, which may be combined with the previous one, the renewable energy source may comprise a wind farm having at least one wind turbine 33 suitable for converting wind energy into electricity.

According to an exemplary embodiment, the furnaces 11 are each suitable for supplying approximately 5 MW of power, so that the furnaces 11 can be powered substantially exclusively by energy supplied by the alternative energy sources 16, at least when in operation. Twenty or more wind turbines 33 may be provided.

According to embodiments, at least one alternator 36 configured to generate alternating electrical energy may be provided.

For example, according to the embodiment described with reference to FIG. 3 , at least one electrical energy storage device 37 is connected between the at least one alternative energy source 16 and the power device 12 .

The storage device 37 stores the electrical energy produced by the renewable energy sources 32, 33 when the renewable energy sources 32, 33 are not being used to power the furnace 11, and stores it for later use. configured to be ready for use. By way of example, storage device 37 may include a battery of capacitors or a supercapacitor.

In the case of an alternating electrical energy source, the storage device 37 may include respective rectifiers and alternators arranged upstream and downstream of the capacitor bank and configured to rectify and respectively convert alternating current and alternating voltage. can.

According to another embodiment, which is described with reference to FIGS. 4, 5 and 7 and which can be combined with the previous embodiments, the at least one alternative energy source 16 provides a direct voltage U _DC and a direct current I _DC A source of direct current electrical energy 34 configured to provide a direct current may be provided.

According to embodiments, the DC electrical energy source 34 may be directly connected to the intermediate circuit 27 downstream of the rectifier 23 .

According to embodiments, a unidirectional electrical component 38 may be provided that is configured to ensure unidirectionality of the current generated. This prevents the wrong polarity input current I _DC from damaging the power unit 12 components.

Unidirectional electrical component 38 may be, for example, a diode or diode circuit.

According to a possible solution, the DC electrical energy source 34 is a renewable energy source comprising a plurality of photovoltaic panels 35 suitable for converting solar energy into electrical energy.

According to embodiments, a number of photovoltaic panels suitable for obtaining power on the order of 100 MW or more can be provided so that the melting and/or heating plant 10 can be adequately powered. can.

In this case, the direct voltage U _DC and the direct current I _DC need only be converted by the converter 24 into the alternating supply voltage Ua and the alternating supply current Ia.

For example, according to embodiments described with reference to FIG. 5, an electrical energy storage device 37 may be provided connected between the at least one alternative energy source 16 and the power device 12 .

Said one or more alternative energy sources 16 may be provided in the immediate vicinity of the area in which the load to be powered is located, in this example in the immediate vicinity of the area in which the arc furnace 11 is located, or as described above. It can also be placed hundreds of meters or even kilometers from the load.

One embodiment described using FIG. 7 has an electric arc furnace 11 located at a first location S1 and at least one alternative energy source 16 located at a second location S2; The second location S2 is for example located at a distance D of 500m to 2000m from the first location S1.

In this embodiment, it can be cumbersome to provide a suitable sized cable to carry the current from the second location S2 to the first location S1.
In practice, the photovoltaic panels 35, which are generally arranged in a plurality of parallel strings, have a DC voltage of about 1500 V, as they must supply sufficient energy to power the electric arc furnace 11. , which generates a very large current.
Thus, for distances D of the order of 500-2000 m, it is necessary to provide cables with very large cross-sections, which can also entail considerable energy losses.

In the embodiment of Figure 7, the electrical energy supply means (13) comprises a conversion device 41 which converts the direct current electrical energy supplied by the photovoltaic panel 35 into alternating current AC. It is configured to convert alternating current AC energy for delivery to the first location S1.

In this way energy can be delivered with negligible losses even over long distances without the need to oversize the cables, facilitating the fabrication and installation of connections in the melting and heating plant 10. can.
In this case, the alternative energy source 16 and the power device 12 may be connected using one or more cables 40 of medium or high voltage alternating current.

Corresponding to the first location S1, the electrical energy supply means 13 comprise a rectifier circuit 42, such as a rectifier bridge, for converting the energy from alternating current to direct current.

Downstream of the converter 41 there may also be a step-up transformer 43 for stepping up the normally low voltage output producing voltage of the converter 41 to a medium or high voltage value.
For example, step-up transformer 43 may be configured to provide an output voltage on the order of several kV (typically 11, 22 or 33 kV).

In this case, a corresponding step-down transformer 44 can be provided, which converts the voltage of the electrical energy supplied via the cable 40 to a medium or high voltage value corresponding to the value of the voltage in the intermediate circuit 27. It is suitable for stepping down the voltage to
If a rectifier bridge 42 is present, a step-down transformer 44 can preferably be placed upstream of the rectifier bridge 42 .

In other embodiments not shown, alternating current energy can be fed directly to the transformer 20, optionally after being transformed using a step-down transformer 44 if desired.

According to a further embodiment, the at least one alternative energy source 16 includes non-renewable energy sources configured to obtain electrical energy by burning fossil fuels, the non-renewable energy sources including gas turbines, or selected from a group that includes an auxiliary generator powered by coal or oil.

According to embodiments, two or more alternative energy sources 16 of the same or possibly different forms may be provided.

For example, according to the embodiment shown in FIG. 6, a first alternative energy source 16 _AC comprising a first alternating electrical energy source 31 connected to the transformer 20 of the power unit 12 and an intermediate circuit 27 A second alternative energy source 16 _DC comprising a direct current electrical energy source 34 may be provided.

Thanks to the structure of the power unit, it is possible to connect multiple alternative energy sources 16 with respective AC energy sources 31 or DC energy sources 34 without the need for additional components.

However, it is clear that the DC electrical energy source 34 can be connected to the transformer 20 with suitable converters provided between them for converting the DC voltage U _DC and DC current I _DC into AC voltage U _AC and AC current I _AC . is.

Conversely, by providing a rectifying device suitable for converting the alternating voltage U _AC and the alternating current I _AC into a direct voltage U _DC and a direct current I _DC , the alternating electrical energy source 31 can be transferred to the intermediate circuit 27 or the unit 28. It is also possible to connect

For example, according to the embodiments described with reference to FIGS. 1 and 6, the melting and/or heating plant 10 is powered by an electrical grid 15 and one or more alternative energy sources 16, 16 _AC , 16 _DC , respectively. One or more parameters are monitored, including the operating state, quality, energy availability and/or cost of the electrical energy supplied, and the amount of energy required by the furnace 11 to provide electrical energy to the power unit 12. a management unit 39 configured to select one, the other or both to supply the .

Availability means the amount of energy produced and/or stored by alternative energy source 16 .

Energy costs are based on grid 15 tariffs, based on time slots of use if different timeslots of use are associated with different costs, costs of raw materials etc. based on management costs of alternative energy sources 16. can be calculated based on For example, for non-renewable energy sources, it can be calculated based on the cost of oil or coal.

According to an embodiment, the melting and/or heating system 10 is associated with at least one alternative energy source 16 and measures the amount of energy produced by one or more renewable energy sources 32, 33, 35 and/or A counter device configured to monitor can be included.

According to embodiments, the melting and/or heating plant 10 includes devices suitable for detecting and/or estimating the energy power absorbed by the furnace 11 over time and providing this information to the management unit 39. be able to.

Depending on the detected conditions, i.e. the amount of energy produced each time by the alternative energy source 16 and possibly stored in one or more storage devices 37, the management unit 39 controls the supply means 13 It can be decided whether to use only the grid 15 as a power source, only the at least one alternative energy source 16, or both.

In particular, the management unit 39 can be configured to select only the supply means 13 necessary on the one hand to ensure correct operation of the melting and/or heating plant 10 each time. On the other hand, the overall energy consumption is optimized, especially by reducing the energy supply by the grid 15 .

According to a further embodiment, the power device 12 has a control command unit 25 configured to control and command the operation of the converter 24 and adjust the alternating supply voltage and supply current supplied to the electrodes 18 over time. Prepare.

According to embodiments, the control command unit 25 may control the converter 24 to selectively set the parameters of the alternating supply voltage Ua and the supply current Ia.

According to embodiments, the control command unit 25 may control the converter 24 to selectively set the parameters of the AC supply voltage Ua and the AC supply current Ia.

Specifically, the feed voltage "Ua" and feed current "Ia" are selectively adjusted in relation to the melting power involved.

According to a possible embodiment, transformer 20 , rectifier 23 connected to transformer 20 and converter 24 together define power supply module 29 .

According to embodiments, the power unit 12 may comprise a plurality of power supply modules 29 connected in parallel to the electrical grid 15 and the electric furnace 11 .

According to embodiments, the power supply module 29 may be connected in parallel to the at least one alternative energy source 16 and the electric furnace 11 .

The combination of several supply modules 29 makes it possible to obtain a power unit arrangement 12 scalable in dimensions for the specific size of the furnace 11 that has to be supplied.

According to a possible embodiment, the control command unit 25 commands all power supply modules 29 to control at least the respective converters 24 such that each module supplies the same values of voltage, current and frequency to the electrodes 18 . It is connected to the. In this way, it is possible to avoid malfunctioning of the entire system.

According to a possible embodiment, power device 12 may include an inductor 30 configured to obtain the desired overall reactance of the device.

Inductor 30 may be connected downstream of converter 24 and is sized to achieve the desired total equivalent reactance. In this way it is possible to obtain the overall reactance given by the contribution of the inductor 30 and by the reactance introduced by the conductors connecting the power device 12 to the furnace 11 or in this case to the electrodes 18. be.

In general, inductance is a (design) parameter and cannot be changed once the component is built.

By changing the frequency (e.g. for a mains supply of 50 Hz), with the same inductance, the reactance value that the component assumes in the circuit can be changed, thus reaching the desired total equivalent reactance value. can.

According to a possible embodiment, in the case of an electric arc furnace 11 the control and command unit 25 may also be connected to the moving device 19 allowing adjustment of the position of the electrodes 18 .
Relationships with the various stages of the merger process.

In particular, the electrode 18 is moved by a handling device 19 in order to track the position of the material and thus change the length of the arc.

In this way, the control command unit 25 can manage and command at least the following parameters for a particular stage of the process: supply voltage Ua, supply current Ia, supply frequency fa, electrode 18 if present Position of.

Possibility to control various parameters, thus optimizing the transfer of energy to the process while reducing the impact on the alternative energy source 16 due to rapid changes in power on the grid 15 and/or furnace side can.

The embodiments described herein also refer to a method of supplying the furnace 11 of the melting and/or heating plant 10 with a metallic material M.

According to an embodiment, the method comprises supplying electrical energy to the power device 12 by means of the supply means 13 and converting the electrical energy by means of the power device 12 to produce an alternating supply voltage Ua and an alternating supply current Ia provided to the furnace 11. get

According to embodiments, the method includes:
- supply of primary voltage Up and primary current Ip to transformer 20 via distribution network 15;
- The primary voltage Up and the primary current Ip are converted by the transformer 20 into the secondary voltage Us and the secondary current Is.
- The secondary voltage Us and the secondary current Is are rectified by a plurality of rectifiers 23 to obtain a DC voltage Ui and a DC current Ii.
using a plurality of converters 24 to transform the DC voltage Ui and the DC current Ii into an AC supply voltage Ua and an AC supply current Ia selectively settable by a control command unit 25 connected to the converter 24;
- Supplying the furnace 11 with the supply voltage Ua and the supply current Ia.

According to an embodiment, the method includes at least one independent alternative energy source 16 connected to the power device 12 different from the electrical grid 15, in addition to or alternatively to the electrical energy supplied by the electrical grid 15. , provides for supplying electrical energy to the furnace 11 .

According to embodiments, the method includes the availability of energy supplied by the grid, energy costs, and the degree of integration of energy available from alternative sources necessary to cover the energy requirements of the furnace 11. detecting one or more parameters to use one or the other or both of the electrical grid 15 and the at least one alternative energy source 16 to power the power device 12; Any one or more of the above parameters are used to define .

According to an embodiment, a power supply method may provide using an alternating electrical energy source 31 to supply alternating voltage U _AC and alternating current I _AC directly to the transformer primary 21 .

According to an embodiment, the power supply method may use a DC electrical energy source 34 to directly supply a DC voltage U _DC and a DC current I _DC to the DC intermediate circuit 27 downstream of the rectifier 23 .

Modifications and/or additions of parts or steps may be made to the melting and/or heating plant 10 and power supply method described above without departing from the scope of the invention as defined by the claims. is clear.

Also, although the present invention has been described with reference to a few specific examples, those skilled in the art will appreciate many other forms of melting and/or heating plant 10 and power supply methods having the features recited in the claims. can certainly be realized with equivalent forms, and therefore all fall within the scope of protection defined by the claims.

Claims (15)

A plant for melting and/or heating a metallic material (M),
a furnace (11), electrical energy supply means (13) and a power unit (12) connected between said supply means (13) and said furnace (11),
The power device (12) comprises:
- connected to the distribution network (15) and adapted to receive an alternating primary voltage (Up) and a primary current (Ip) and convert them into an alternating secondary voltage (Us) and an alternating secondary current (Is); at least one transformer (20),
- connected to said transformer (20) and adapted to convert said alternating secondary voltage (Us) and said alternating secondary current (Is) into a DC intermediate voltage (Ui) and a DC intermediate current (Ii); a plurality of rectifiers (23);
a plurality of converters (24) connected on one side to said rectifier (23) and on the other side to said furnace (11), said DC intermediate voltage (Ui) and said DC intermediate current (Ii); into an alternating supply voltage (Ua) and an alternating supply current (Ia) supplied to said furnace (11),
said alternating supply voltage (Ua) and said alternating supply current (Ia) are selectively settable by a control command unit (25) connected to said converter (24),
The electrical energy supply means (13) comprises:
at least one alternative energy source (16) separate from said electrical grid (15) and connected to said power device (12), said power device (12) being connected to said power distribution; comprising an alternative energy source (16) configured to supply energy for powering the furnace (11), additionally or alternatively to the electrical energy supplied by the grid (15). A plant characterized by said at least one alternative energy source (16) comprises an alternating electrical energy source (31) configured to supply alternating voltage (U _AC ) and alternating current (I _AC );
said alternating energy source (31) is connected to said transformer (20);
The plant according to claim 1, characterized in that: The transformer (20) comprises a transformer primary (21) and a transformer secondary (22) magnetically coupled to the transformer primary (21),
3. Plant according to claim 2, characterized in that the source of alternating electrical energy (31) is connected to the transformer primary (21). Said alternating current electrical energy source (31) is a renewable energy source selected from a hydroelectric power station or a dam (32) suitable for converting hydroelectric energy into electrical energy or wind energy into electrical energy. 3. A wind power plant comprising at least one wind turbine (33) suitable for and at least one alternator (36) adapted to generate alternating electrical energy. 3. The plant according to 3. said at least one alternative energy source (16) comprising:
a DC electrical energy source (34) configured to supply a DC voltage (U _DC ) and a DC current (I _DC );
5. Any one of claims 1 to 4, characterized in that said DC electrical energy source (31) is connected to an intermediate circuit (27) of said power unit (12) downstream of said rectifier (23). 1. The plant according to item 1. 6. A source of direct current electrical energy (34) according to claim 5, characterized in that it is a renewable energy source comprising a plurality of photovoltaic panels (35) suitable for converting solar energy into electrical energy. plant. The furnace (11) is located at a first location (S1) and the alternative energy source (16) is at a second location located at a distance of 500m to 2000m from the first location (S1). (S2),
said electrical energy supply means (13) comprises one or more cables (40) of medium or high voltage alternating current connecting said alternative energy source (16) and said power device (12);
7. Plant according to claim 5 or 6. Said electrical energy supply means (13) comprises a conversion device (41) for converting said electrical energy from direct current to alternating current corresponding to said second location (S2), and a converter (41) for converting said electrical energy from alternating current to said first a rectifier circuit (42) configured to convert to direct current at a location (S1) of
A plant according to claim 7. at least one electrical energy storage device (37) connected between said at least one alternative energy source (16) and said power device (12) and used to power said furnace (11) 7. A device according to claim 4 or 6, characterized in that it comprises at least one electrical energy storage device (37) adapted to allow storage of the energy produced by said renewable energy source when not. plant. said at least one alternative energy source (16) comprises a non-renewable energy source configured to obtain electrical energy by burning fossil fuels;
10. A plant according to any one of the preceding claims, characterized in that said non-renewable energy source is selected from the group comprising gas turbines or auxiliary current generators. comprising a management unit (16),
Said management unit (16) controls the operating state, quality, quantity and/or cost of electrical energy available from said electrical grid (15) and said at least one alternative energy source (16) and said furnace (11) monitoring one or more parameters of the amount of energy required by
configured to select one, the other or both to supply electrical energy to said power unit (12) and thus to supply electrical energy to said furnace (11) at least depending on each operating state and total energy cost. 11. Plant according to any one of claims 1 to 10, characterized in that The transformer (20), the rectifier (23) and the converter (24) constitute a power supply module (29),
a plurality of said power supplies connected in parallel with each other, said power unit (12) between said grid (15) and said furnace (11) and between said alternative energy source (16) and said furnace (11). 12. Plant according to any one of the preceding claims, characterized in that it comprises a module (29). A method of supplying electrical energy to a furnace (11) of a plant (10) for melting and/or heating metallic materials, comprising:
supply means (13) for supplying electrical energy to the power unit (12), said power unit ( 12) converting the electrical energy using
The method includes:
- supplying the transformer (20) with primary voltage (Up) and primary current (Ip) using the distribution network (15);
- conversion of said primary voltage (Up) and primary current (Ip) into secondary voltage (Us) and secondary current (Is) using said transformer (20);
- rectification of said secondary voltages (Us) and secondary currents (Is) with a plurality of rectifiers (Is) to obtain direct voltages (Ui) and direct currents (Ii);
- said converters (24) to said alternating supply voltage (Ua) and said alternating supply current (Ia) selectively settable by means of a control command unit (25) connected to a plurality of converters (24); conversion of the direct voltage (Ui) and the direct current (Ii) used;
- supplying said feed voltage (Ua) and feed current (Ia) to said furnace (11);
in a method comprising
Additionally or alternatively to the electrical energy supplied by said electrical grid (15), at least one alternative energy source (16) independent of said electrical grid (15) and said power device (12 ), supplying electrical energy to said furnace (11) by means of at least one alternative energy source (16) connected to said furnace (11). one of operating conditions, energy availability and cost of energy supplied by said electrical grid (15) and said alternative energy source (16) and the amount of electrical energy required by said furnace (11). detecting and/or monitoring the above parameters;
the power distribution network for powering the power unit (12) and thus powering the furnace (11) in response to at least the detected condition and/or the amount of energy required by the furnace (11); 14. A method according to claim 13, characterized by determining whether to use one of (15) and said alternative energy source (16), the other, or both. Said alternative energy source (16) comprises a renewable energy source (32, 33, 35) and said method stores energy produced by said renewable energy source (32, 33, 35) in at least one storage device. 15. A method according to claim 14, characterized in that it is stored at (37) so that it can be used at a later time.

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